Steering system and method for autonomous vehicles

1. A steering system for an autonomous vehicle, said steering system comprising:

a steering mechanism having a steering mechanism input member and a steering mechanism output member, said steering mechanism being configured to translate rotation of said steering mechanism input member into movement of said steering mechanism output member which is configured to affect the position of a steer tire of said autonomous vehicle, thereby affecting the lateral position of said autonomous vehicle;

a steering wheel which provides a mechanical input to said steering mechanism input member from an operator of said autonomous vehicle;

a steering actuator which rotates to apply torque to said steering mechanism, thereby inducing movement of said steering mechanism output member which affects the position of said steer tire of said autonomous vehicle; and

a variable coupling member operatively between said steering actuator and said steering mechanism which is configured to vary the torque that can be transmitted from said steering actuator to said steering mechanism.

2. A steering system as in claim 1 further comprising:

an autonomous driving electronic control unit; and

an input device which provides navigational input data to said autonomous driving electronic control unit;

wherein said autonomous driving electronic control unit is configured to process said navigational input data to generate navigational output data which is transmitted to said steering actuator and to said variable coupling member, thereby rotating said steering actuator and varying the torque that can be transmitted from said steering actuator to said steering mechanism.

3. A steering system as in claim 1 wherein said steering mechanism is a rack and pinion steering gear.

4. A steering system as in claim 3 wherein said steering mechanism input member is a pinion gear and said steering mechanism output member is a rack.

5. A steering system as in claim 1 wherein said variable coupling member is a magnetorheological fluid coupling.

6. A steering system as in claim 1 further comprising a means for selectively coupling and decoupling said steering wheel from said steering mechanism input member.

7. A steering system as in claim 6 further comprising:

an autonomous driving electronic control unit; and

an input device which provides navigational input data to said autonomous driving electronic control unit;

wherein said autonomous driving electronic control unit is configured to process said navigational input data to generate navigational output data which is transmitted to said steering actuator, said variable coupling member, and said means for selectively coupling and decoupling said steering wheel from said steering mechanism input member, thereby rotating said steering actuator, varying the torque that can be transmitted from said steering actuator to said steering mechanism, and coupling and decoupling said steering wheel from said steering mechanism input member as determined necessary.

8. A method for operating a steering system for an autonomous vehicle where said steering system includes a steering mechanism having a steering mechanism input member and a steering mechanism output member, said steering mechanism being configured to translate rotation of said steering mechanism input member into movement of said steering mechanism output member which is configured to affect the position of a steer tire of said autonomous vehicle, thereby affecting the lateral position of said autonomous vehicle; a steering wheel which provides a mechanical input to said steering mechanism input member from an operator of said autonomous vehicle; a steering actuator which rotates to apply torque to said steering mechanism, thereby inducing movement of said steering mechanism output member which affects the position of said steer tire of said autonomous vehicle; and a variable coupling member operatively between said steering actuator and said steering mechanism, said method comprising:

adjusting said variable coupling member to vary the torque that can be transmitted from said steering actuator to said steering mechanism.

9. A method as in claim 8 wherein said steering system also includes an autonomous driving electronic control unit and an input device which provides navigational input data to said autonomous driving electronic control unit, said method further comprising:

using said autonomous driving electronic control unit to process said navigational input data to generate navigational output data which is transmitted to said steering actuator;

using said navigational output data to rotate said steering actuator; and

using said navigational output data to vary the torque that can be transmitted from said steering actuator to said steering mechanism.

10. A method as in claim 8 further comprising coupling and decoupling said steering wheel from said steering mechanism input member.

11. A method as in claim 8 , said method further comprising:

providing navigational input data to an autonomous driving electronic control unit of said steering system;

using said autonomous driving electronic control unit to process said navigational input data to generate navigational output data;

using said navigational output data to rotate said steering actuator;

using said navigational output data to vary the torque that can be transmitted from said steering actuator to said steering mechanism; and

using said navigational output data to couple and decouple said steering wheel from said steering mechanism input member.

12. A method as in claim 8 further comprising:

decoupling said steering wheel from said steering mechanism input member; and

adjusting said variable coupling member to increase the torque that can be transmitted from said steering actuator to said steering mechanism based on an actual or expected decoupling of said steering wheel from said steering mechanism input member.

13. A method as in claim 8 further comprising:

coupling said steering wheel to said steering mechanism input member; and

adjusting said variable coupling member to decrease the torque that can be transmitted from said steering actuator to said steering mechanism based on an actual or expected coupling of said steering wheel to said steering mechanism input member.

14. A method as in claim 8 further comprising:

switching said steering system from a manual mode of operation where said operator of said autonomous vehicle controls the lateral direction of said autonomous vehicle through said steering wheel to an autonomous mode of operation where an autonomous driving electronic control module is primarily responsible for the lateral direction of said autonomous vehicle; and

varying the torque that can be transmitted from said steering actuator to said steering mechanism based on an actual or expected switching from said manual mode of operation to said autonomous mode of operation.

15. A method as in claim 8 further comprising:

switching said steering system from an autonomous mode of operation where an autonomous driving electronic control module is primarily responsible for the lateral direction of said autonomous vehicle to a manual mode of operation where said operator of said autonomous vehicle controls the lateral direction of said autonomous vehicle through said steering wheel; and

varying the torque that can be transmitted from said steering actuator to said steering mechanism based on an actual or expected switching from said autonomous mode of operation to said manual mode of operation.

16. A method as in claim 15 wherein said step of varying the torque that can be transmitted from said steering actuator to said steering mechanism includes setting the torque that can be transmitted from said steering actuator to said steering mechanism to a magnitude that can be overcome by said operator of said autonomous vehicle through said steering wheel.